The Mendell laboratory works at the leading-edge of RNA biology and cancer biology, investigating noncoding RNA functions, the roles of noncoding RNAs in tumorigenesis, and the application of RNA-based tools to elucidate noncoding RNA and tumor biology. We have made major contributions to our understanding of the roles of noncoding RNAs in cancer, with a particular focus on the microRNA (miRNA) pathway. Our early work in this area demonstrated that miRNAs function as critical components of key oncogenic and tumor suppressor networks, including the MYC, KRAS, and p53 pathways. My laboratory has been at the forefront of elucidating miRNA functions in vivo and translating these findings into novel therapeutic approaches, most notably through our demonstration that systemic delivery of miRNAs potently suppresses tumorigenesis in mouse cancer models without toxicity. We have also advanced our understanding of miRNA regulation, identifying examples of regulated miRNA biogenesis and decay. Looking ahead, this is a particularly important and exciting time for exploring the interface of RNA biology and tumor biology. After more than a decade of research into the roles of miRNAs in cancer, our understanding of how miRNAs contribute to tumorigenesis in vivo is still surprisingly limited. There is thus a great nee for the derivation and analysis of novel in vivo models of miRNA gain- and loss-of-function. We have also learned that perturbations of miRNA maturation, either through mutations in components of the miRNA biogenesis machinery or through aberrant activity of specific miRNA regulatory pathways, are a common feature of human malignancies. Nevertheless, precisely how miRNA maturation is regulated in cancer remains poorly understood. Beyond the miRNA pathway, we now know of the existence of thousands of long noncoding RNAs (lncRNAs) that participate in diverse cellular and developmental functions in mammals. Emerging data implicate an important role for lncRNAs in cancer, but we are at the earliest stages of understanding the underlying mechanisms. Finally, the emergence of powerful RNA-based tools for genome editing has provided unprecedented opportunities for functional analysis of noncoding RNAs in vivo. Based on these gaps in our knowledge and new research opportunities, the next phase of our research will focus on 1) the analysis of miRNA functions in normal physiology and cancer in vivo using novel gain- and loss-of-function mouse models; 2) investigation of the regulation of miRNA processing in normal development and tumorigenesis; 3) elucidation of lncRNA functions in normal physiology and cancer using cellular and animal models; and 4) application of CRISPR-based genomic editing to illuminate noncoding RNA functions in cells and animals and to discover and validate novel regulators of malignancy-associated phenotypes. My laboratory is uniquely positioned to synthesize these areas of research and thereby continue our track record of sustained productivity and leadership within the noncoding RNA and cancer biology communities.